The present invention relates to tape cassettes for recording audio or video signals or computer data, and more specifically to a write protect device or erroneous erase preventing device.
As shown in FIGS. 20xcx9c24, a tape cassette 101 includes a pair of rotatable tape reels 103 and 104 winding magnetic tape 102, and a cassette body (or case) 105 enclosing the tape reels 103 and 104. At one corner of a lower face 106 of the cassette body 105, there is provided an erroneous erase preventing device (or write protect device) 111 for discriminating a record enable state enabling the recording on the magnetic tape 102 and for preventing recorded data from being erased by error.
The erroneous erase preventing device 111 consists of a detectable portion 112 for discrimination to prevent erroneous erasing (which serves as a detectable portion formed in the bottom 106 of the cassette body 105), and an erroneous erase preventive plug 113 serving as a discrimination plug for opening and closing the detectable portion 112.
The detectable portion 112 is formed by opening a round hole in the bottom 106 of the case 105.
As shown in FIG. 22, the erroneous erasing preventive plug 113 has an open-close portion 114 for opening and closing the detectable portion 112, a slide operating portion 115, and a lock portion 116.
As shown in FIG. 20, the erroneous erasing preventive plug 113 is right-left slidably attached in the cassette body 105 in the state that the slide control portion 115 projects out of an operation opening 108 on the back 107 of the cassette body 105. Thus, the plug 113 is slidable in a right and left direction.
The erroneous erasing preventive plug 113, when the slide operation element 115 is operated to slide to one direction, closes the detectable portion 112 with the open-close portion 114 as shown in FIG. 23, while the lock portion 116 engages in a first lock opening 109 provided inside the case 105 to keep the closing state of the detectable portion 112.
Also, the erroneous erasing preventive plug 113, when operated to slide to direction A shown by an arrow from the state shown in FIG. 23, opens the detectable portion 112 which was closed by the open-close portion 114 as shown in FIG. 24, while the lock element 116 hooks to a second lock opening 110 provided inside the cassette body 105 to lock to keep the opening state of said detectable portion 112.
Then, if the tape cassette 101 is loaded in the recorder-player that is not shown in figures, while in the state that the detectable portion 112 for discrimination to prevent erroneous erasing is closed by the erroneous erasing preventive plug 113, the erroneous erase detecting element provided on the recorder-player is prevented by the erroneous erasing preventive plug 113 from being lead into the cassette body 105 from the detectable portion 112, which enables the recording on the magnetic tape 102 in the tape cassette 101.
Also, if the tape cassette 101 is loaded in the recorder-player, while in the-state that the detectable portion 112 is open, the erroneous erasing detection element provided on the recorder-player is lead into the cassette body 105 from the detectable portion 112, which disables the recording on the magnetic tape 102 in the tape cassette 101 or, in other words, prevents erroneous erasing.
By the way, in addition to the conventional tape cassette (hereinafter called the first format tape cassette) 101 shown in FIGS. 20-24, the tape cassette that enables high-density recording on the magnetic tape (hereinafter called the second format tape cassette) has also been developed.
As shown in FIG. 25, the second format tape cassette 201, like the first format tape cassette 101, is provided with a pair of tape reels 203 and 204 with magnetic tape 202 wound around them that are rotatably accommodated in the cassette body 205, and, in one corner in the bottom 206 of the cassette body 205, there is provided with an erroneous erasing preventive device 211.
The erroneous erasing preventive device 211 consists of a detectable portion 212 for discrimination or identification to prevent erroneous erasing and an erroneous erasing preventive plug 213 which closes/opens the detectable portion 212.
The detectable portion 212 is formed by opening a round hole in the bottom 206 of the cassette body 205.
The erroneous erasing preventive plug 213 is formed roughly in the same way as the erroneous erasing preventive plug 113 of the first format tape cassette 101, and when it is operated to slide to one direction, closes the detectable portion 212, while when it is operated to slide to the other direction, releases open the detectable portion 212.
The cassette body 105 of the first format tape cassette 101 is also used as the cassette body 205 of the second format tape cassette 201.
The detectable portion for identification to prevent erroneous erasing 212 of the second format tape cassette 201 is formed, near the detectable portion 112 for identification to prevent erroneous erasing of said first format tape cassette 101, with a predetermined spacing D between the portion 212 and the portion 112.
Because of the development of magnetic materials and the reduction in thickness of magnetic recording layers enabled by the recent technological advances, the third format tape cassette that enables higher-density recording than said second format tape cassette 201 has also been developed.
By the way, in attempting to use, as the cassette body of the third format tape cassette, the cassette body 205 of the second format tape cassette 201, the following problems have been arisen.
(1) As shown in FIG. 26, in attempting to form the detectable portion for identification to prevent erroneous erasing 312 for the third format tape cassette between the detectable portion for identification to prevent erroneous erasing 112 for the first format tape cassette and the detectable portion for identification to prevent erroneous erasing 212 for the second format tape cassette provided on the bottom 306 of the cassette body 305 of the third format tape cassette 301, these three detectable portions 112, 212 and 312 become close in distance, therefore, as shown in FIG. 27, the thickness t of the separating walls 321 between the detectable portions 112, 212 and 312 become thinner, which often results in defective products during forming process and reduces efficiency in production. Moreover, the separating walls 321 are easy to break during usage.
(2) If the detectable portion 312 for the third format tape cassette of the cassette body 305 is formed sufficiently away from the detectable portions 112 and 212, the above-mentioned first problem (1) will be solved. However, the bottom plate 306 of said cassette body 305 is formed with various holes such as detection hole for magnetic tape type 331, cassette positioning holes 332 and 333, detection hole for recording format 334, detection hole for tape end 335. Therefore, there are imposed constraints in space. Also, in the case that the detectable portion 312 for the third format tape cassette is formed at a distance from the detectable portions 112 and 212, the position of the detection element for erroneous erasing of the recorder-player unit must also be moved in conformity with the position of the detectable portion 312 for the third format tape cassette. Again, on the recorder-player unit, the change of the position of the detection element for erroneous erasing is also subjected to constraints in space, and difficulties in terms of cost.
From the above viewpoints, it is desirable to form the detectable portions for identification to prevent erroneous erasing 112, 212 and 312 for the first, second, and third format tape cassettes together in a single space of the cassette body 305.
Therefore, it is an object of the present invention to provide tape cassettes having a plurality of discriminating detectable portions formed closed in a narrow area.
According to the present invention, a tape cassette comprises: a casing formed with a plurality of discriminating detectable portions; and a discriminating plug slidably disposed in the casing, for moving into and out of at least one of the discriminating detectable portions. The discriminating detectable portions are collectively formed in a single cavity, and the discriminating plug faces at least one of the discriminating detectable portions in the recess.